Photostructurable body and process for treating a glass and/or a glass-ceramic

ABSTRACT

The invention relates to a photostructurable body, in particular glass or glass-ceramic, in which the glass is a multicomponent glass and/or the glass-ceramic is a multicomponent glass-ceramic, in each case having a positive change in refractive index Δn as a result of the action of light.

[0001] The invention relates to a photostructurable body, which inparticular comprises glass or glass-ceramic or consists of thesesubstances, in accordance with the preamble of claim 1 or 18, to aprocess for treating a glass and/or glass-ceramic in accordance with thepreamble of claim 22 and to objects having a body of this type.

BACKGROUND OF THE INVENTION

[0002] Optical components, which are based on the guidance andmanipulation of light through structures, such as waveguides andgratings, are already known, for example in the sensor technology andtelecommunications sectors. The primary medium for wave guidance iscurrently optical fibers; however, planar components are becoming moreimportant on account of increased demands for miniaturization andincreased complexity. The advantage of planar components is thepossibility of producing a multifunctional component on just a singlechip and thereby, for example, minimizing the coupling losses and alsothe production-related outlay for different components and therefore thecosts of these components. Although bifunctional or multifunctionalcomponents can also to a certain extent be produced in fibers, forexample suitably doped fused silica (SiO₂), in particular Ge-doped SiO₂,is already being used for the production of Bragg gratings as(de)multiplexers, for example in wavelength filtering or for sensors infibers. In this case, UV irradiation is used to produce an inhomogeneousdefect distribution in the Ge-doped glass, and this, by changing theabsorption coefficient, leads to changes in the refractive index. Thesegratings or other structures can also be produced in a similar way incertain Pb—, RE- (RE=Rare Earth) and Ag-doped glasses. Furthermore,suitable conditioning processes can be used for the targetedprecipitation and subsequent selective etching of the microcrystalswithin the irradiated regions, as for example in the case of Corning8603 Fotoform/FotoCeram or Hoya PEG-3.

[0003] It is also known that by irradiating different glasses withsuitable high-energy pulses (fs pulses), it is possible to producestructures in glass. For example, positive changes in the refractiveindex in the range up to 10⁻² have been produced by the fs writing ofGe-doped SiO₂ glass or fused silica (K. Hirao et al., J. Non-Cryst.Solids 235, pp. 31-35, 1998).

[0004] Negative changes in refractive index have also been observed inborosilicates, sulfide glasses and lead glasses, cf. in this respectCorning WO 01/44871, PCT/US00/20651. By suitably setting the pulseenergy and the writing speed, it is in this case possible to producechanges in refractive index without physically damaging the glass.

[0005] The invention is based on the object of overcoming conventionallimitations on structuring using light and of providing materials andprocesses which in particular allow the direct writing of waveguidestructures.

[0006] This object is achieved, in a surprisingly simple way, by meansof the features described in claims 1, 18 and 22.

[0007] The invention for the first time, in a particularly advantageousand surprising way, describes a material which is not fused silica, butrather provides a wide class of glasses having the positive change inrefractive index Δn which is advantageously desired.

[0008] A particularly preferred embodiment comprises an LAS glass(lithium-aluminosilicate glass).

[0009] A further particularly preferred embodiment results if the glassis an LAS glass-ceramic (lithium-aluminosilicate glass-ceramic).

[0010] A preferred LAS glass and/or LAS glass-ceramic has a compositionof from 15 to 90% by weight of SiO₂, from 1 to 35% by weight of Al₂O₃,from 1 to 20% by weight of Li₂O.

[0011] A particularly preferred LAS glass and/or LAS glass-ceramic has acomposition of from 20 to 85% by weight of SiO₂, from 5 to 35% by weightof Al₂O₃, from 1 to 18% by weight of Li₂O.

[0012] The most preferred composition comprises from 25 to 75% by weightof SiO₂, from 5 to 30% by weight of Al₂O₃, from 2 to 15% by weight ofLi₂O.

[0013] To increase the sensitivity or photosensitivity, it isadvantageous for the glass and/or glass-ceramic to comprise a sensitizerand/or activator which is preferably selected from the group consistingof Ce, Er, Eu, ions and mixtures thereof. As an alternative or inaddition, the glass and/or glass-ceramic may comprise a photosensitiveelement or a mixture of photosensitive elements which are preferablyselected from the group consisting of Cu, Ag, Au, Ce³⁺, Eu²⁺ and thefurther ions and mixtures thereof, in order in this way to provideabsorption centers which are preferably suitable.

[0014] The sensitivity can advantageously be increased further if theglass and/or glass-ceramic in addition or as an alternative compriseshalides which are preferably selected from the group consisting of F,Br, Cl, I and ions and mixtures thereof.

[0015] In a further embodiment, the glass and/or glass-ceramic compriseslithium silicate crystal phases and/or beta-quartz solid solutionfractions or structures.

[0016] In a further embodiment, the glass and/or glass-ceramicadvantageously comprises lithium disilicate and/or lithium metasilicateand/or keatite.

[0017] For the change in the refractive index brought about during thestructuring, it is useful if the glass and/or glass-ceramic comprises Aghalide crystallites and/or clusters, since this too makes it possible toprovide interaction areas for the light which is introduced.

[0018] In a further embodiment the glass and/or glass-ceramic comprisessilver or gold clusters.

[0019] As an alternative or in addition, the glass and/or glass-ceramic,after the structuring, comprises two-dimensional and/orthree-dimensional structures which are preferably produced by at leastpartially destroying the crystallites by means of fs irradiation.

[0020] In a particularly preferred embodiment, the glass and/orglass-ceramic comprises a dopant which has an energy position,preferably demonstrated by its absorption, which is located within aband gap of the glass.

[0021] If the dopant provides absorption centers for the absorption oflight which can be bleached out and can be used to influence therefractive index of the glass, it is possible to effect a change in therefractive index even using light of a wavelength lying in the visibleregion of the spectrum, with the result that the intensity required forthe structuring can be reduced.

[0022] To treat a glass and/or a glass-ceramic as described in claim[lacuna], it is possible for the structuring using light to comprise aphotostructuring step using fs light pulses, in particular fs laserlight pulses, which make it possible to achieve a particularly highdegree of homogeneity of the resultant structure.

[0023] To produce two-dimensional and/or three-dimensional structures bymeans of photostructuring, a subsequent thermal and/or chemicaltreatment, in particular an etching treatment, may be very useful, sincestructured regions often have a different chemical reactivity or analtered etching rate.

[0024] It is also advantageous to produce silver or gold clusters usingthe process according to the invention; in this case, the glass and/orglass-ceramic comprises silver or gold fractions.

[0025] The invention is described in more detail below on the basis ofpreferred embodiments and with reference to the appended figures, inwhich:

[0026]FIG. 1 shows a first exemplary embodiment 1, in which, unlike thewaveguides made from SiO₂ and other known glasses which have alreadybeen written using fs laser light pulses, the waveguides in an LAS glasshave an ideal round shape,

[0027]FIG. 2 shows a second exemplary embodiment 2, in which, unlike thewaveguides made from SiO₂ and other known glasses which have alreadybeen written using fs laser light pulses, the waveguides in some of theLAS glasses have an ideal round shape; in the case of glass 2, thescattered light fraction is particularly low,

[0028]FIG. 3 shows an example of the negative change in refractive indexexhibited by glasses with a negative Δn, wherein dark “anti-waveguides”having two bright flanks to the left and right of the actual structureare revealed on examination under a microscope; these flanks may form asa result of strain-induced changes in refractive index,

[0029]FIG. 4 shows typical positive changes in refractive index in fusedsilica,

[0030]FIG. 5 shows the third exemplary embodiment, glass 7 from Table 1,

[0031]FIG. 6 shows a model image illustrating the refractive indexdistribution in glasses with a negative Δn and for comparison withexperimentally acquired results which are presented in FIGS. 1 to 5 andthe tables which follow,

[0032]FIG. 7 shows a graphical representation of the calculation of therefractive index profile by means of the densification theory for anexcerpt from the positive change in refractive index from 0 to +10⁻³, inparticular for comparison with experimentally acquired results presentedin FIGS. 1 to 5 and in the tables which follow,

[0033]FIG. 8 shows a graphical representation of the calculation of therefractive index profile by means of the densification theory for anexcerpt from the negative changes in refractive index on a scale from−10⁻³ to 0, in particular for comparison with experimentally acquiredresults presented in FIGS. 1 to 5 and in the tables which follow.

DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention comprises the use of LAS glasses andglass-ceramics for the production of microstructured components, inwhich structuring is carried out with the aid of light, preferably withthe aid of laser light.

[0035] Furthermore, the invention comprises the structuring of LAS glasswhich contains suitable sensitizers, such as for example Ce, Eu, Er,ions and mixtures thereof. Rare earth-doped glasses which contain Eu²⁺and/or Ce³⁺ can be structured either by radiating in UV light, in whichcase photoreduction counts as one possible mechanism (this mechanism isdescribed again separately in the next paragraph), or by means of fsradiation, for example in Er³⁺—, Tm³⁺—, . . . doped glasses: in thiscase, it is possible to produce active waveguides for use as amplifiersor lasers.

[0036] The invention also relates to LAS glass, which containsphotoreducible ions, such as Ag, Au, Cu, or photooxidizable ions, suchas Eu²⁺ or Ce³⁺, etc.

[0037] Furthermore, the invention also comprises LAS glass whichcontains polyvalent heavy metal and metal cations, such as for examplePb, Sb, Sn, Bi, Fe, etc. Cations such as Pb and Sn in this case act asphotosensitive activators or sensitizers.

[0038] With the aid of UV radiation, it is in this case possible toproduce gratings or structures with a high change in refractive indexattributable to the formation of surface reliefs. Highly refractivestructured glasses can be used for applications in the field of digitaloptical elements, DOEs.

[0039] The invention also comprises the writing of the abovementionedglasses using intensive light.

[0040] Furthermore, the invention comprises the writing of these glassesusing UV radiation.

[0041] Moreover, the invention relates to the writing of these glassesusing ultra-short (fs) pulses.

[0042] A person skilled in the art will be able to adapt the writingparameters, such as laser wavelength, pulse duration and pulse power, insuch a way that the change in refractive index can be set appropriately.In this context, it is appropriate to make use of the existingabsorption bands in the glass and thereby to accurately set the transferof energy required to change the refractive index. One simple approachwhich is possible is for the laser wavelength divided by an integer mwhere m≧1 to lie in a wavelength region which has a sufficientabsorption which is significantly different than 0. In this context,local absorption maximums or absorption bands are particularly suitable.

[0043] By suitably utilizing two-photon or three-photon resonances, asdescribed in the US application entitled “Resonantly EnhancedPhotosensitivity” in the name of the applicant Schott Corporation,Yonkers, N.Y. from the same application date as the present application,which is hereby incorporated in its entirety by reference in the subjectmatter of the present invention, it is possible to achieve higherpenetration depths or structure depths, which represents an importantparameter with regard to the component efficiency in particular, forexample, in the case of DOEs.

[0044] Furthermore, a person skilled in the art, by suitably doping theglass, can set the nature and level of the change in refractive index ina suitable way. In a first approach, the doping can be calculated fromthe level of absorption values desired, it being possible for this levelto be suitably determined by means of simple tests, and the absorptioncan be correspondingly increased by increasing the doping.

[0045] A suitable thermal aftertreatment can lead to phase changes orprecipitation of microcrystallites in the glass, and these can be usedfor the dimensionally accurate etching of microcomponents.

[0046] A suitable thermal aftertreatment can lead to the precipitationof microcrystallites in the glass, resulting in characteristicallycolored structures in the glass.

[0047] A suitable thermal aftertreatment can lead to the precipitationof nanocrystallites, such as Li disilicate or metasilicate in the glass,which also ensure a sufficient transparency of the material.

[0048] A heat treatment process for this purpose comprises aconditioning process which is first of all carried out at a relativelylow temperature, meaning that the body is heated from room temperatureat a rate of approx. 5° C. per min and is then held at approximately500° C. for approx. 60 min, in order to produce crystals or to developcrystal nuclei.

[0049] Then, higher temperatures of 605° C. are used after a temperaturerise at approx. 3° C. per min has been carried out.

[0050] This is followed by cooling to room temperature at approx. 5° C.per min in order for the structures to be etched out.

[0051] According to the invention, it is also possible to perform just asingle conditioning step, after which nanocrystals which continue toleave the glass transparent are already present. During the second stepdescribed, which is also known as the growth step, the size of thenanocrystals is significantly increased, so that they form clusters.

[0052] After the first conditioning step alone, nanocrystals havediameters of approx. 30 to 40 nm and do not scatter the light. After thesecond growth step, the crystals become larger, cause the light to bescattered and may even make the glass opaque, depending on the durationof the heat treatment.

[0053] Depending on the particular application, it is possible to omitthe first step, in order then to obtain fewer nuclei but largercrystals.

[0054] It is also possible to omit the second step, in order then toobtain fewer but more homogeneously distributed crystals.

DETAILED DESCRIPTION OF THE INVENTION

[0055] In the following detailed description, all the percentages arepercentages by weight, unless otherwise indicated.

[0056] Furthermore, in the context of the invention, the termmulticomponent glass is to be understood as meaning any glass which doesnot consist just of SiO₂ (fused silica), but rather includes more thanone glass component.

[0057] In the context of the invention, a positive change in refractiveindex Δn is to be understood as meaning an increase or rise in therefractive index value, in particular in the magnitude or measurablevalue of the refractive index.

[0058] In a particularly preferred form of the invention, LAS glasses(lithium aluminosilicate glass) are used to write in structures, such asfor example waveguides and gratings, by means of (laser) light. Theglass can be used for the production of optical and other componentswhich are based on 2D and 3D microstructuring.

[0059] This allows structuring by changing the refractive indeximmediately after the irradiation by changing the density d or thevolume per unit weight and the absorption coefficient α(λ), and bythermal and/or chemical treatment, such as for example etching,following the exposure.

[0060] Bodies which have been structured in this manner can be used aspart of a waveguide, waveguide laser and/or optical amplifier, as partof sensors (applications inter alia in Bragg gratings: multiplexers,demultiplexers or as a filter or optical data store, and also DOEs.Hidden or desired visible marking by means of structuring steps of thisnature is also possible.

[0061] The glass used substantially comprises SiO₂, Al₂O₃ and Li₂O. Theglass preferably contains from 15 to 90% of SiO₂, on a weight basis, asa network-forming agent.

[0062] The aluminum oxide content is between 1 and 35% of Al₂O₃. Thiscan be used, inter alia, to set the chemical resistance of the glass.With higher A1₂0₃ contents, the glass tends to crystallize, which is notruled out according to the invention but is merely less preferred. TheLi₂O content is between 1 and 20%.

[0063] If the material is used in crystallized form or is crystallizedor partially crystallized after laser writing, Li is an importantcomponent of the main crystalline phases, such as for examplebeta-quartz solid solution, keatite, virgilite, petalite, eucryptite,spodumene or mixtures thereof. Furthermore, however, it is also possiblefor secondary phases, such as for example quartz, cristobalite orberlinite to occur.

[0064] Even if not all the phases are optically transparent orcompletely transparent, there are applications in the non-opticalsector, for example MEMs or micromechanical applications, which do notnecessarily require transparent material.

[0065] It is particularly preferable for a glass according to theinvention to contain from 20 to 85% of SiO₂, from 3 to 27% or 5 to 35%of Al₂O₃ and from 2 to 20% or 1 to 18% of Li₂O. It is very particularlypreferable for the glass according to the invention to contain from 25to 85% or 25 to 75% of SiO₂ , from 5 to 25% or 5 to 30% of Al₂O₃ andfrom 5 to 20% or 2 to 15% of Li₂O.

[0066] Furthermore, the glass may contain from 0 to 50% of P₂O₅, from 0to 40% of B₂O₃, from 0 to 20% of alkali metal apart from Li, R₂O, R═Na,K, and alkaline-earth metal where R═Mg, Ba, Sr.

[0067] Further components which may be present include sensitizers, suchas Ce₂O₃, Er₂O₃, Eu₂O₃, etc., photooxidizable and photoreducibleelements, such as Ag⁺, Cu^(+/2+), Au⁺, Eu²⁺, Ce³⁺, and other suitableelements.

[0068] The glass may also contain thermal stabilizers and refiningagents, such as Sb₂O₃, As₂O₃, etc.

[0069] Furthermore, the glass may also contain halides, such asfluorine, chlorine and/or bromine.

[0070] Different crystalline phases, such as for example Li disilicateand metasilicate, keatite, virgilite, beta-quartz solid solution,keatite solid solution, petalite, cristobalite, etc., can be produced bysuitable heat treatment.

[0071] Since, for example, virgilite or beta-quartz solid solution havea negative coefficient of thermal expansion, it is possible, by suitablyselecting the glass composition and suitably adjusting the crystallinephase, to set the thermal expansion in a very wide range of expansionsfrom less than 0 to greater than 10 ppm. In particular, it is possibleto produce what are known as “zero-expansion materials” or “athermal”materials.

[0072] Doping

[0073] The glass according to the invention can be structured in a widerange of ways by suitably selecting the doping and irradiation source.Therefore, depending on the particular doping and type of irradiation, aperson skilled in the art could bring about increases in the refractiveindex or reductions in the refractive index in order to producewaveguides or gratings or other microstructures. Furthermore, bysubsequent heat treatment, the irradiated area can be deliberatelycolored or ceramicized, for example by doping with Ag and halogen atomsor halides. The light-induced production of chemically unstablecrystallites (e.g. lithium disilicate or metasilicate) in the glassmakes it possible to produce structures in three dimensions.

[0074] fs Irradiation

[0075] WO 01/09899 A1 has disclosed the direct writing of wave-guidingstructures into a glass substrate. For this purpose, a femtosecond laserpulse (e.g. Ti:sapphire laser system, wavelength 800 nm, 80 fs pulseduration, 1 kHz repetition rate, laser power adjustable up to 500 mW) isfocused into a silicate glass in order for it to be heated to more than1380 Kelvin at certain points. Furthermore, DE 101 55 492 A1 in the nameof the same applicant gives an extensive description of the writing ofchanges in refractive index and is incorporated in its entirety byreference in the subject matter of the present application andprotective rights which are subsequently derived therefrom.

[0076] Writing Process

[0077] In detail, the laser beam is passed through suitable beam-shapingand guidance optics, comprising mirrors, filters and a microscopeobjective, before ultimately being focused into the glass. The incomingbeam is split by a beam splitter with preferably 60% reflection and 40%transmission.

[0078] The power is in this case continuously monitored by a powermeter. To prevent the optics from being destroyed by the high laserpower, it is possible for the beam to be reduced by suitable grayfilters (e.g. NG10 or a combination of NG5 +NG9). The beam is thenfocused into the specimens by means of the microscope objective. Thedesired structures can then be produced in the glass by translationalmovement of the specimen relative to the beam.

[0079] JP 09311237, EP 797 112, EP 1 045 262, U.S. Pat. No. 6,154,593and U.S. Pat. No. 5,978,538 describe, for example, the formation ofoptical waveguides in glass substrates.

[0080] However, investigations carried out by the inventors have shownthat for different glasses, in particular LAS glasses, there aredifferent sets of writing parameters, meaning different combinations ofwriting speed, pulse length, wavelength and power, which lead to optimumresults.

[0081] These values are easy for a person skilled in the art to find byfirst of all, at an available wavelength and pulse length, increasingthe power until initial changes in refractive index occur. Then, he canvary the pulse length and the power in such a way that the changes inrefractive index of the desired level are achieved.

[0082] To write waveguides, the person skilled in the art can adapt thewriting speed with a fixed laser pulse power in such a way that thepunctiform structures fuse together to form waveguides which are asideal as possible. If the writing speed is to be increased, the laserpulse power has to be correspondingly increased as well. If the writingspeed is to be reduced, the laser pulse power has to be correspondinglyreduced as well. However, modifications of this nature lie within thescope of the average person skilled in this field.

[0083] Typical ranges for the writing speed are in this case, forexample, 125 to 250 μm/s. Higher writing speeds could also be achievedby increasing the laser repetition rate from kHz to MHz.

[0084] As a result of the waveguides being written, it is usuallypossible to observe stresses occurring at the sides of the waveguides.

[0085] These stresses lead to reductions in the refractive index if thestructure is a waveguide or to increases in the refractive index if itis an anti-waveguide which has a negative Δn.

[0086] Structures of this type can be recognized even under a lightmicroscope, therefore in the case of waveguides bright dashes or ideallydots which are flanked by dark areas and in the case of anti-waveguidesas dark dots or dashes flanked by two bright areas, as illustrated inFIGS. 1 and 3.

[0087] The inventors' current explanation for the advantageous effectsof the invention involve a physical and thermal approach for describingthe glass transition, although this does not necessarily have to bephysically correct, but rather is merely intended to serve as a possibleexplanation model to provide a better understanding of the surprisingexperimental results which have been discovered.

[0088] An FEM analysis using the ABAQUS FEM program was used in order toprovide initial answers to this question.

[0089] In the inventors' current model, it is assumed that the glasstransition at high heating and cooling rates can be described by aTool-Narayanaswamy model. Model data are extrapolated to hightemperatures and high heating rates.

[0090] The heating step will describe a thermal source intensitydistribution which is dependent on the position. The shape of thisheated volume resembles an ellipsoid. On account of the symmetry, anaxially symmetrical or cylinder-symmetrical geometry was used in orderto represent the geometric conditions in the glass in model form.

[0091] After the first step, which comprised 100 femtoseconds, ofcalculation of the temperature maximum, the result was an imaginarycalculated temperature of approx. 2500 Kelvin in the center of theellipsoid.

[0092] On account of the very high heating rates, this imaginarytemperature does not have to coincide with the actual, real temperature,but at the end of the step the imaginary temperature in the region ofthe center of the ellipsoid is substantially equal to the realtemperature.

[0093] In the second step, the heated ellipsoid is cooled by theenvironment by means of heat conduction.

[0094] After ten microseconds, imaginary temperature and visco-elasticstresses are produced. This results in the following effects orinfluences on the refractive index.

[0095] There are two effects on the local refractive index:

[0096] 1. Compression on account of the differing local temperature orits temporal profile, which leads to a locally different imaginarytemperature. This effect is an isotropic effect.

[0097] 2. Photoelasticity which results from the stresses which remainafter cooling. This effect is direction-dependent and is therefore anisotropic effect.

[0098] The compression as a result of the FEM analysis using the ABAQUSFEM program is represented in the figures.

[0099] There are two types of glass.

[0100] The first is described by a positive structural expansioncoefficient α_(STR), in which the thermal expansion of the “liquid”glass is higher than the thermal expansion of the “solid” glass. In thiscase, the compression is arranged in the center of the hot spot. Outsidethe hot zone there are volumes with material which is less under stressor pressure. The compression results from the center toward the outerside in a dish-like arrangement. There are dishes with a high degree ofcompression and dishes with a small degree of compression toward theoutside. The result is refractive index distributions as illustrated byway of example in FIG. 7 and represented successfully by the waveguidesshown in FIGS. 1 and 2, which are illustrated as seen from the end sideand show the intensity distribution which results during the conductionof light.

[0101] Glasses with a negative structural expansion coefficient have theopposite effect. The hot spot is placed under less pressure and outsidethe hot center there are dishes which are more strongly compressed orcompacted.

[0102] Then, butterfly-like figures of pressurized glass, as illustratedby way of example in FIG. 8 and experimentally reproduced successfullyby the anti-waveguide shown in FIG. 3, which is illustrated as seen fromthe end and shows the intensity distribution which results during theconduction of light, result outside the hot zone.

[0103] The inventors assume that plasma effects do not occur or do nothave any significant influence at power densities of less than 10¹³ to10¹⁴ watts per cm².

[0104] The standard wavelength of 800 nm is customarily used in fsexperiments. Therefore, in the case of silicate glasses, the startingpoint is a multi-photon absorption process with at least four photonsinvolved, leading to the formation of the waveguiding structures.

[0105] Since the process is a multi-photon process, the change inrefractive index takes place only in the region of the focus, since withthe lasers which are currently available the required photon density isgenerally only available here.

[0106] By suitable manipulation of the specimens, it is thereforepossible to produce 3D structures with a diameter in the region ofapproximately 10 μm within the volume or bulk glass.

[0107] The introduction of the required energy into the glass andtherefore the nature of the change in refractive index is set by asuitable selection of the writing parameters. In this context, it hasproven particularly expedient for the wavelength of the ultrashort pulseto be set in the range of the multi-photon absorption of the glass.However, the utilization of direct resonances with ultrashort pulses canlead to excessive heating and therefore to cracks. Moreover, theseresonances may then also take place outside the focus, which can causethe waveguides to become blurred.

[0108] This multi-photon absorption can be positively influenced bysuitable doping, as described in more detail in the above-cited patentapplication in the name of Schott Corporation, which is incorporated inits entirety by reference in the subject matter of the presentapplication.

[0109] Furthermore, it has proven eminently suitable to set pulsedurations which are as short as possible. Even when the fs laserablation is compared with the ablation by laser in the ps range, it hasbeen found that the structures formed using fs pulses are defined morehomogeneously, more smoothly and more successfully by a multiple.Similar results can be observed when shorter fs pulses are used in thebulk.

[0110] Since more energy is transmitted into the glass per pulse, thestructures can write with a lower total power overall, which is alreadyof economic benefit to the user.

[0111] As has already been mentioned above, by suitable doping it ispossible to set absorption bands in the glass which ensure an evenbetter transmission of energy through resonant multi-photon absorption.By suitable setting of doping and writing parameters, it is thereforepossible to achieve targeted changes in refractive index Δn of up to afew 10⁻².

[0112] Furthermore, the shape of the structures produced can also beinfluenced by the doping. For a positive change in refractive index,reference is made to glasses 1 to 8 and glasses 9 and 10 comprisingkeatite or beta-quartz crystal or beta-quartz solid solution fractionsin Table 1 below.

[0113] Furthermore, by radiating fs pulses into LAS glass which hasalready been ceramicized, it is possible to reverse the ceramicizationstep. It is thereby possible to produce positive or negative changes inthe refractive index in the same glass depending on the preliminarytreatment.

[0114] Certain LAS glasses can be converted into glass-ceramics with anultra-low (zero) expansion by ceramicization before or after themicrostructures have been produced, which is particularly advantageousfor the production of, for example, demultiplexers/multiplexers orsimilar components. To carry out ceramicization steps of this nature,reference is made to extensive literature relating to the ceramicizationof green glass.

[0115] Surprisingly, the inventors have for the first time discoveredthat with femtosecond lasers it has been possible to achieve positivechanges in refractive index in multicomponent glasses, such as forexample LAS glasses and glass-ceramics, in a similar way to those whichhave been achieved in fused silica glasses.

[0116] In other multicomponent glasses, it has hitherto only beenpossible to achieve refractive index profiles with a negative change inthe refractive index.

[0117] Therefore, the invention for the first time makes it possible toachieve direct structuring using light which immediately leads towaveguiding structures in multicomponent glasses.

[0118] Moreover, the fs-written glasses according to the invention had ahomogeneous, round structuring compared to fused silica glasses, whichgenerally had a more dash-shaped form of the waveguides. TABLE 1Exemplary embodiments with results for Δn: “+” corresponds to a positivechange in refractive index, “−” corresponds to a negative change inrefractive index, “+/−” corresponds to a positive change in refractiveindex for green glass and a negative change in refractive index forceramic, “?” corresponds to values which are still to be determined inmore detail. Examples 1 2 3 4 5 6 % by % by % by % by % by % by weightweight weight weight weight weight SiO₂ 65.6 78.5 78.8 78.6 78.6 69.9Ag₂O 0.2 0.2 0.2 0.1 CeO₂ 0.3 0.3 0.1 0.1 Sb₂O₃ 0.5 0.5 0.5 0.6 0.5 0.6B₂O₃ 3.5 0.2 0.2 0.2 0.2 0.2 Al₂O₃ 12.7 4.2 4.3 4.2 4.2 3.5 Li₂O 9.3 9.69.6 9.5 9.6 4.8 Na₂O 1.8 1.7 1.7 1.7 1.7 18.2 K₂O 3.9 4.0 4.0 4.0 4.0ZnO 2.3 1.0 1.0 1.0 1.0 3.7 P₂O₅ CaO BaO As₂O₃ TiO₂ ZrO₂ MgO SnO 0.1 Br2.6 F 3.0 Delta n (+) (+) (+) (+) (+) Example 7 8 9 10 11 12 % by % by %by % by % by % by weight weight weight weight weight weight SiO₂ 58.181.0 65.6 57.9 63.0 64.4 Ag₂O 0.2 0.1 CeO₂ 0.1 0.0 Sb₂O₃ 0.4 0.9 0.8 0.4B₂O₃ Al₂O₃ 22.8 3.9 21.4 25.4 12.5 14.9 Li₂O 3.5 9.2 3.6 3.7 6.2 6.2Na₂O 1.0 0.8 0.2 0.8 9.0 9.7 K₂O 3.8 0.6 0.3 ZnO 1.9 0.9 1.6 1.2 5.5 4.1P₂O₅ 4.9 7.2 CaO 1.9 BaO 2.6 2.3 As₂O₃ 0.5 0.6 TiO₂ 0.1 2.3 2.4 ZrO₂ 1.81.6 3.0 MgO 1.0 0.1 SnO Br F Crystal HQMK/ HQMK/ phase keatite keatiteDelta n (+) 1.5 × 10⁻³ +/− +/− ? ?

[0119] UV Structuring

[0120] As well as with ultrashort pulses, it is also possible to producechanges in refractive index by radiating light of a certain wavelengthinto suitably doped glasses and thereby bringing about photooxidations,photoreductions, defect centers or similar reactions in the glass. Inthis case, light is preferably radiated into the range of absorption ortwo-photon absorption of the glass doped with suitable sensitiveelements.

[0121] The redox reactions can in this case be produced directly bylight, for example using the absorption centers Eu²⁺, CE³⁺ or by the useof suitable redox pairs, such as for example Ce³⁺/Ag⁺. The change inabsorption or density produced by photoreactions then causes acorresponding change in the refractive index.

[0122] The Schott glass foturan can also be used for this purpose, butwithout Ce, instead with a silver reduction via other polyvalent ions,such as for example refining agents As, Sb or impurities (Fe, Cr, . . .). Compared to exposure using UV lamps, lasers have higher intensities,so that special activators, such as Ce, can be present in lowerconcentrations or can be eliminated altogether.

[0123] The magnitude of the change in refractive index and the depth ofthe altered region can be controlled by suitably setting the beamintensity and the doping.

[0124] “True” 3D structuring, in which, as with the fs structuring,waveguides and similar structures can be produced in the glass, can beachieved by determining the threshold. The threshold is in this caseexceeded either by beam bundling, for example by focusing, or byoverlapping the foci of a plurality of beams.

[0125] In the case of the former method, it is advantageous inparticular to make use of two-photon resonances, since in this case theglass is structured only in the center of the focus.

[0126] To provide sufficient photons for this process, in this case useis made of a ps laser. Two-photon absorption generally takes place viawhat is known as a virtual intermediate state.

[0127] Since there is only a relatively low probability of this “state”being occupied and a further photon must be available instantaneously,so as to ultimately bring about the transition into the real finalstate, a high energy density or photon density is required, and this isnot normally present with cw lasers, even at high intensities.Therefore, a short-pulse laser is used for this type of structuring.

[0128] The use of a preferably localized real intermediate state for theTPA (two photon resonance) increases the transition probability.Moreover, the lifespan of this real state is longer, so that more timeis available to achieve the desired final state by means of a furtherphoton. In this case, therefore, it would be possible to dispense withthe use of a short-pulse laser.

[0129] Furthermore, it is also possible for a wide range of refractiveindex profiles to be produced by homogenizing the beam intensity orperforming other suitable adjustments to the intensity profile.

[0130] Crystallites and clusters, which can be used either for selectiveetching of the irradiated glass (e.g. lithium disilicate and lithiummetasilicate) or for local coloring (e.g. Ag halide clusters), can beproduced in the irradiated glass by suitable conditioning steps.

[0131] Preferred glasses for the UV structuring are given in Table 2.

[0132] The structures produced can be used both for micro-opticalcomponents and for photonic components and also for micromechanicalcomponents and for permanent, individual marking or labeling of theproduct.

[0133] Examples of applications for the optical components includewaveguides, diffractive optical elements, gratings for sensors or forwavelength selection, waveguide lasers, etc. Micromechanical applicationfields would lie in the microfluidics sector (valves, connection stubs,nozzles, reaction chambers), and for electronic substrates. A furtherapplication lies in the field of optical data storage. TABLE 2 Preferredexemplary embodiments for UV-structurable glass compositions (% byweight) Particularly Claims: Preferred: preferred: Oxide Min Max Min MaxMin Max SiO₂ 15 90 20 85 25 75 Al₂O₃ 1 35 5 35 3 27 Li₂O 1 20 1 18 2 15Na₂O 0 20 0 20 0 18 K₂O 0 20 0 15 0 10 MgO 0 20 0 15 0 10 CaO 0 20 0 150 10 ZnO 0 30 0 25 0 10 SrO 0 30 0 25 0 10 BaO 0 40 0 30 0 10 PbO 0 60 050 0 40 B₂O₃ 0 40 0 30 0 25 P₂O₅ 0 50 0 45 0 15 TiO₂ 0 45 0 30 0 10Ta₂O₅ 0 45 0 30 0 10 ZrO₂ 0 55 0 40 0 10 La₂O₃ 0 55 0 40 0 10 F 0 8 0 60 5 Cl 0 15 0 10 0 8 Br 0 18 0 15 0 10 I 0 20 0 18 0 15 Ag 0 20 0 18 0 5CuO 0 10 0 8 0 5 Au 0 10 0 8 0 5 As₂O₃ 0 8 0 5 0 4 Nb₂O₅ 0 10 0 8 0 5Nd₂O₃ 0 10 0 8 0 5 Yb₂O₃ 0 10 0 8 0 5 Er₂O₃ 0 10 0 8 0 5 Eu₂O₃ 0 10 0 80 5 CeO₃ 0 10 0 8 0 5

1. A photostructurable body, in particular comprising glass orglass-ceramic, wherein the glass is a multicomponent glass and/or theglass-ceramic is a multicomponent glass-ceramic, in each case having apositive change in refractive index An as a result of the action oflight.
 2. The photostructurable body as claimed in claim 1, wherein theglass is an LAS glass (lithium-aluminosilicate glass).
 3. Thephotostructurable body as claimed in claim 1, wherein the glass is anLAS glass-ceramic (lithium-aluminosilicate glass-ceramic).
 4. Thephotostructurable body as claimed in claim 1, wherein the LAS glassand/or the LAS glass-ceramic comprises a composition of from 15 to 90%by weight of SiO₂, from 1 to 35% by weight of Al₂O₃, from 1 to 20% byweight of Li₂O.
 5. The photostructurable body as claimed in claim 4,wherein the composition comprises from 20 to 85% by weight of SiO₂, from5 to 35% by weight of Al₂O₃, from 1 to 18% by weight of Li₂O.
 6. Thephotostructurable body as claimed in claim 4, wherein the compositioncomprises from 25 to 75% by weight of SiO₂, from 5 to 30% by weight ofAl₂O₃, from 2 to 15% by weight of Li₂O.
 7. The photostructurable body asclaimed in one of claims 1 to 6, wherein the glass and/or glass-ceramiccomprises a sensitizer and/or activator which is preferably selectedfrom the group consisting of Ce, Er, Eu and ions and mixtures thereof.8. The photostructurable body as claimed in one of claims 1 to 7,wherein the glass and/or glass-ceramic comprises a photosensitiveelement or a mixture of photosensitive elements which are preferablyselected from the group consisting of Cu, Ag, Au, Ce³⁺, Eu²⁺, polyvalentheavy metal and metal cations, such as for example Pb, Sb, Sn, Bi, Feand the further ions and mixtures thereof.
 9. The photostructurable bodyas claimed in one of claims 1 to 8, wherein the glass and/orglass-ceramic comprises a suitable sensitizer and activator, Ce, Erand/or Eu, and ions thereof, and a photosensitive element, Cu, Ag and/orAu and/or ions thereof.
 10. The photostructurable body as claimed in oneof claims 1 to 9, wherein the glass and/or glass-ceramic compriseshalides which are preferably selected from the group consisting of F,Br, Cl, I and mixtures thereof.
 11. The photostructurable body asclaimed in one of claims 1 to 10, wherein the glass and/or glass-ceramiccomprises lithium silicate crystal phases.
 12. The photostructurablebody as claimed in one of claims 1 to 10, wherein the glass and/orglass-ceramic comprises beta-quartz solid solution fractions orstructures.
 13. The photostructurable body as claimed in one of claims 1to 12, wherein the glass and/or glass-ceramic comprises lithiumdisilicate.
 14. The photostructurable body as claimed in one of claims 1to 12, wherein the glass and/or glass-ceramic comprises lithiummetasilicate.
 15. The photostructurable body as claimed in one of claims1 to 12, wherein the glass and/or glass-ceramic comprises keatite. 16.The photostructurable body as claimed in one of claims 1 to 15, whereinthe glass and/or glass-ceramic comprises Ag halide crystallites and/orclusters.
 17. The photostructurable body as claimed in one of claims 1to 16, wherein the glass and/or glass-ceramic comprises silver or goldclusters.
 18. The photostructurable body as claimed in one of claims 1to 17, wherein the glass and/or glass-ceramic comprises two-dimensionaland/or three-dimensional structures which are preferably produced by atleast partially destroying the crystallites by means of fs irradiation.19. A photostructurable body, in particular as claimed in claim 1,wherein the glass and/or glass-ceramic comprises a dopant which has anenergy position, preferably demonstrated by its absorption, which islocated within a band gap of the glass.
 20. The photostructurable bodyas claimed in claim 19, wherein the dopant provides absorption centersfor the absorption of light.
 21. A photostructurable body, in particularas claimed in claim 20, wherein the dopant provides absorption centersfor the absorption of light which can be bleached out and can be used toinfluence the refractive index of the glass.
 22. The photostructurablebody as claimed in claim 21, wherein the absorption centers for theabsorption of light effect a positive change in the refractive indexunder the action of light.
 23. A process for treating a glass and/orglass-ceramic, comprising the use of a multicomponent glass forstructuring using light.
 24. The process for treating a glass and/orglass-ceramic as claimed in claim 23, comprising the use of LAS glass(lithium aluminosilicate glass) for structuring using light.
 25. Theprocess for treating a glass and/or glass-ceramic as claimed in claim23, comprising the use of LAS glass-ceramic (lithium aluminosilicateglass-ceramic) for structuring using light.
 26. The process for treatinga glass and/or glass-ceramic as claimed in one of claims 23 to 25,comprising the use of a sensitizer and/or activator, such as inparticular Ce, Er, Eu and ions thereof, for the photostructuring. 27.The process for treating a glass and/or glass-ceramic as claimed in oneof claims 23 to 26, wherein the structuring using light comprises aphotostructuring step using laser light.
 28. The process for treating aglass and/or glass-ceramic as claimed in claim 27, wherein thestructuring using light comprises a photostructuring step using fs lightpulses, in particular fs laser light pulses.
 29. The process fortreating a glass and/or glass-ceramic as claimed in one of claims 23 to28, for producing two-dimensional and/or three-dimensional structures bymeans of photostructuring and/or subsequent thermal and/or chemicaltreatment, in particular etching.
 30. The production of lithium silicatecrystal phases using the process as claimed in one of claims 23 to 28.31. The production of beta-quartz solid solution using the process asclaimed in one of claims 23 to 28 together with a subsequentconditioning step.
 32. The production of lithium disilicate using theprocess as claimed in claim
 30. 33. The production of lithiummetasilicate using the process as claimed in claim
 31. 34. Theproduction of Ag halide crystallites and/or clusters using the processas claimed in one of claims 23 to 28, in which the glass and/orglass-ceramic comprises Ag halides.
 35. The production of silver or goldclusters using the process as claimed in one of claims 23 to 28, inwhich the glass and/or glass-ceramic comprises silver or gold fractions.36. The use of an LAS glass-ceramic for producing two-dimensional andthree-dimensional structures by at least partial destruction ofcrystallites in the LAS glass-ceramic by means of fs irradiation. 37.The use of the body as claimed in one of claims 1 to 22 for UVstructuring.
 38. The use of the body as claimed in one of claims 1 to 22for UV laser structuring.
 39. The use of the body as claimed in one ofclaims 1 to 22 for fs laser structuring.
 40. An object which has beenstructured using light, in particular a waveguide, a waveguide laser, anoptical amplifier, sensors, an optical multiplexer, an opticaldemultiplexer, an optical filter, an optical data store, comprising thebody as claimed in one of claims 1 to 22.